Pulping apparatus

ABSTRACT

A rotor assembly for use in pulping apparatus is similar in general construction to the disclosure of Vokes U.S. Pat. No. 3,073,535, but the thickness of its defibering vanes is reduced to minimize their pumping action, and pumping vanes are provided on the outer surfaces of certain of the defibering vanes to increase the vortical circulation effect created by the rotor in operation.

United States Patent 1191 1111 3,889,885 Couture June 17, 1975 [54] PULPING APPARATUS 2.363 5; 11x32? SENIZ'OOCI 2241/4665 x 3, ,5 l oes 4l4 .ll {75] Inventor: wall" Ctmmre Dorval 3,085,756 4/1963 Danforth Ct al. .5 241/4617 x Canada 3,145,936 8/1964 Monks 11 241/4617 [73] Assignee: The Black Clawson Company,

Middletown, Ohio Primary Examiner-Granville Y. Custer, Jr. [22] Filed Jan 11 1974 Attorney. Agent, or Firm-Biebel, French & Bugg [2!] Appl. No: 432,576 [57} ABSTRACT A rotor assembly for use in pulping apparatus is simi- [52] 241/4617 lar in general construction to the disclosure of Vokes H Int Cl Bozc 13/28 US. Pat. No. 3,073,535, but the thickness of its defi- [58] Fieid l I 46 17 bering vanes is reduced to minimize their pumping ac- 2.41/29 l tion, and pumping vanes are provided on the outer surfaces of certain of the defibering vanes to increase References Cited the vertical circulation effect created by the rotor in UNITED STATES PATENTS 7/1942 Wells 241/46 X operation.

6 Claims, 12 Drawing Figures PATENTEIJJUN 17 m5 ,889.8 85

SHEET 1 PRIOR ART FIG 1 BACKGROUND OF THE INVENTION This invention relates to pulping apparatus for liquid slurry stocks such as paper making stock, and more particularly to rotors for use in such pulping apparatus.

The invention has special relation to pulping apparatus of the type wherein the stock to be pulped is contained in a tub which is provided with a rotor or impeller mounted in the bottom or side wall thereof for rotation on an axis causing outward circulatory movement of the stock in a generally vortical pattern which creates hydraulic shearing forces in the stock and thereby effects the desired pulping or defibering action. Pulping apparatus of this general type is employed in both batch and continuous operations, and the invention is equally applicable to both types of operation.

In the experience of the present inventor, the rotors having the most effective defibering action for the uses outlined above are constructed in accordance with Vokes U.S. Pat. No. 3,073,535. As pointed out in that patent, however, the pumping action ofthe rotor is provided only by the leading edge surfaces of its vanes and is therefore maintained in close proximity to the cooperating bedplate. As a result, the defibering action, which is caused both by hydraulic shear in the zone above the rotor and by mechanical action between the rotor and bedplate, is extremely effective, but only a relatively small volume of stock is subjected to this action during any given time interval, and the power requirements for adequate treatment of a given batch or for a given period of continuous operation are relatively high.

Another result of the limiting pumping action of the rotors of the Vokes patent construction is that because it is primarily confined to the vicinity of the bedplate, it may not develop a complete vortex in the stock above the rotor, especially if the liquid level is relatively high. This in turn can lead to a tendency for floating material to remain on or near the surface of the stock without reaching the vicinity of the rotor for subjection to its defibering action.

The objective of the present invention is therefore to provide a rotor of improved construction which is capable of defibering action equal to that of the rotors of the Vokes patent construction, which maintains its high effectiveness over a wide range of consistencies, and which will operate at relatively low power requirements per volumetric unit on a batch basis and per time interval on a continuous basis.

Summary of The Invention The principles of the invention are best explained in connection with the description of the preferred embodiments, but they can be summarized as comprising primarily two modifications of the rotor construction shown in the Vokes patent, namely, decrease in the axial dimensions (thickness) of the defibering vanes, and addition of true circumferential pumping vanes on the outer surface of the rotor to increase its pumping action without sacrifice of its defibering ability while maintaining its power requirements lower than for a rotor of the same diameter of the Vokes patent construction.

Brief Description Of The Drawings FIG. I is a fragmentary view in prospective illustrating a rotor of the Vokes patent construction and its 00 operating bedplate;

FIG. 2 is a fragmentary section on the line 2-2 of FIG. I and on a larger scale;

FIG. 3 is a plan view ofa rotor constructed in accordance with the invention;

FIG. 4 is an enlarged section on the line 44 of FIG.

FIG. 5 is a fragmentary view taken as indicated by the line 5-5 of FIG. 3 and on a larger scale;

FIG. 6 is an enlarged fragmentary section on the line 66 of FIG. 5;

FIG. 7 is a view similar to FIG. 6 but showing a modi fied construction;

FIG. 8 is a view similar to FIG. 3 showing another rotor constructed in accordance with the invention;

FIG. 9 is a partial section taken as indicated by the line 99 of FIG. 8;

FIGS. 10 and 11 are fragmentary views similar to FIG. 8 and showing further modifications of the invention; and

FIG. 12 is a veiw similar to FIG. 4 showing another modification of the invention.

Description Of The Preferred Embodiments FIGS. 1 and 2 show one commercial form of rotor 10 constructed in accordance with the Vokes patent and a cooperating perforated bedplate 11 such as are installed in the bottom or side wall of a pulper tub. For convenience, the surface of the rotor which is adjacent the bed plate will be referred to hereinafter as the under surface, and the exposed surface will be referred to as the upper surface, irrespective of the orientation of the rotor axis. The rotor 10 includes a hub (not shown) on which are mounted the vane ring 13 and smoothly domed cover plate 15. Each of the vanes 20 is of essentially the configuration shown in FIG. 2, comprising a bottom surface 21 substantially parallel with the bedplate II, but including a trailing portion 22 curved away from the bedplate. The top surface 23 of each vane 20 is curved smoothly from its leading edge to meet the trailing edge of the bottom surface, and the flat leading face 25 which connects the surfaces 2I and 23 is tilted forwardly and downwardly toward the surface ofthe bedplate, commonly at an angle in the range of 5 to 15.

In operation this rotor is maintained with a fixed axial clearance between the vane under surfaces 21 and the bedplate ll, e.g. one-eighth inch, and the leading faces 25 of the vanes serve several purposes. In the first place, they constitute the only pumping means on the rotor for producing centrifugally outward flow of the stock and thus promoting the desired vortical circulation pattern. They are therefore of substantial axial extent (thickness) e.g. 2.00 to 2.25 inches at the outer end, and of increasing thickness toward their radially inner ends in order to provide adequate area for pumping action.

Note also in FIG. 1 that in order to provide adequate space between adjacent vanes through which to expose the surface of the bedplate, and to urge stock into the desired rubbing contact with the bedplate, each face 25 extends tangentially of the rotor in such direction as to form a relatively small angle with a radius to its outermost point, shown as 30. Since this angle is substan tially less than 45, and its complementary angle is correspondingly greater than 45 along the radially outer part of each of faces which has the highest linear velocity, their pumping efficiency is relatively low, and a substantial proportion of the power consumed by the rotor in developing its pumping action is lost so far as useful results are concerned.

In addition to the pumping action of the vane faces 25, their downwardly tilted arrangement has the effect of urging the stock toward the surface of the bedplate so that some of it will pass between the under surface 21 of each vane and the roughened working surfaces of the bedplate provided by the perforations therethrough, the resulting rubbing action on the stock being highly effective in defibering. Still another action of the faces 25 is to apply mechanical force to solid materials in the slurry under treatment in the form of repeated mechanical blows which are in addition to the mechanical rubbing action which takes place in the spaces between the vanes and the bedplate.

The upper surface 23 of each vane also contributes to the defibering action of the rotor, in that the relatively large area of each of these surfaces develops high forces of hydraulic shear in the layer of stock overlying the rotor, due to the differential velocity between the surfaces of the vanes and the stock. Thus this rotor and bedplate combination carries out the desired defibering action by combination of the forces of hydraulic shear, mechanical contact, and rubbing between the vanes and the bedplate. These defibering forces are relatively intense in the zone in which they are created, but this zone is of limited extent, and the rotor is not as effective as could be desired in circulating the stock in such manner as to bring large volumes of stock into the treatment zone in an acceptable short time interval. In other words, this rotor and bedplate combination is highly effective for defibering, but its total power requirements, for pumping and defibering, are relatively high when considered on a per unit volume basis for batch operation or per time interval for continuous op eration.

The rotor in accordance with the invention as shown in FIGS. 37 is of the same general construction as the rotor 10 and is intended for similar installations with a cooperating bedplate. It includes a cover plate 31 and a vane ring 32 which constitutes the main component of the rotor body and supports a similar arrangement of projecting vanes 33. As shown in FIG. 4, however, the thickness of each vane is substantially reduced as compared with that of the vane 20, the comparison being illustrated in FIG. 4 by the dotted line 34 which represents the corresponding section in FIG. 2, and which shows the reduction as of the order of 50 percent. Each vane leading face 35 is therefore of correspondingly reduced area, but it otherwise has the same functions as the leading faces 25 of the vanes 20.

The under surface 36 of each vane 33 is shown as of the same contour as that of the vane 20, including the trailing portion 37. The upper surface 38 is also similar in contour to the corresponding surface of vane 20, but since its attitude is different because of the reduced distance between its leading edge and that of the under surface 36, it appears relatively flat except for the trailing portion 39 which is curved to blend with the trailing edge 37 of the under surface 36.

The primary difference between the rotor 30 and the rotor 10 lies in the provision of pumping vanes 40 on the outer surface of rotor 30, four of these vanes being provided on alternate vanes 33. Each of the pumping vanes 40 is curved about a radius as viewed axially of the rotor and is of substantially greater height than the reduction in thickness of the vanes 33 as compared with vanes 20.

The curvature of each vane 40 and its location on the vane ring are that while its leading end is substantially tangent to a projection of the face 35 of the associated vane, its trailing end extends to a point 41 adjacent the trailing outer corner of the associated vane 33. A tangent to this point 41 will therefore define with a radius from the rotor axis to point 41 a substantially larger angle b, e.g. to than the angle C defined by the face 35 and a radius to its outermost point 42, which is shown as 30. The complement of this angle b, which is designated a and is defined by a radius 44 from the center of curvature of the vane and a radius 45 from the axis of the rotor, will therefore more closely approach the 45 value at which a centrifugal pumping vane operates at highest efficiency.

Tests show that the rotor 30 is fully as effective from the standpoint of its difibering action as a rotor of the same diameter constructed as shown in FIGS. l2. Thus there is essentially the same rubbing action between the under surface of each vane and the cooperating bedplate, and the upper surfaces of the vanes are comparably effective in the development of hydraulic shear in the adjacent zone. Similarly, the front faces of the vanes impart comparable mechanical action to solid materials which they encounter in the stock, the reduction in the thickness of the vanes producing no significant reduction in their ability to apply mechanical force to the stock.

The major distinctions between the operation of the rotor 30 and the prior construction illustrated by FIGS. I-2 lie in the reduction in the power required by the rotor 30 to accomplish the same defibering action on a unit volume or time basis, and the greatly increased pumping efficiency of the rotor 30. This reduction in power appears to be initially a direct result of the reduction in thickness of the vanes, which reduces by a comparable amount the aggregate area of the leading faces of the vanes which have a pumping effect. In fact, this reduction in power appears to be on an essentially straight line basis, so that if each vane is half as thick in the prior construction, the power requirements will similarly be halved.

This initial reduction in the power requirements will of course be offset to some extent by the pumping power required by the pumping vanes 40, but the total power requirements will still be substantially less than for a rotor 10 of the same diameter. It appears that this advantageous result is due to the curvature and location of the vanes 40, especially their radially outer parts, which causes them to be substantially more efficient in their pumping action, on a comparative area basis, than the leading faces 25 of vanes of the construction of FIGS. 1-2.

The practical effect and result of these conditions is that a rotor constructed as shown in FIGS. 3-7 will require substantially less horsepower per ton, for either batch or continuous operation, than a rotor of the same diameter constfllcted as illustrated by FIGS. l-2, to produce substafltlally the same effective defibering action on any of a wide variety of furnishes, ranging all the way from clean broke or pulp lap to waste papers of low and dirty grades, and at any handable consistency. In fact, it appears that the increased centrifugal pumping ability of the rotors of the invention enhances their defibering ability, because the deep vortex which they produce causes the stock to recirculate to the rotor zone from such substantial heights that the momentum with which it impinges on the rotor and bedplate supplements their defibering action.

The dimensions of the defibering and pumping vanes of the rotor 30 are subject to some variation in accor dance with specific desired operating conditions, and only a typical set of values will be given to provide guidance for the benefit of those skilled in the art. In general, it appears that the limiting factor on the thickness of the defibering vanes 33 at their outermost ends is the requirement of sufficient rigidity to withstand all normal working stresses. For example, in a rotor of the construction shown in FIGS. 1-2 having a maximum diameter of 57 inches a typical thickness of each vane 20 at the location shown in FIG. 2 is 2.150 inches, as compared with 7.75 inches for the horizontal dimension.

The same dimensions for a rotor of the invention of the same maximum diameter at the location shown in FIG. 4 may be 1.00 to 1.125 by 7.75 inches, or a reduction of approximately 50 percent in area, while the pumping vanes 40 may have a similar axial dimension of 2 inches or more, e.g. 4 inches. The pumping vanes 40 may extend parallel with the axis of the rotor, as shown in FIG. 6, or they may be inclined in their direction of rotation similarly to the vane faces 38, as shown in FIG. 7, preferably in the angular range of to to provide a downward component to the stock propelled thereby which will supplement the action of the tilted faces of the defibering vanes, at least along their inner portions, in directing stock toward the surface of the bedplate.

FIGS. 8-9 illustrate modifications of the invention in conjunction with a one-piece rotor 50 incorporating radially projecting vanes 51 of essentially the same individual construction as the vanes 33 except that each vane is so arranged that its leading face 52 forms an angle C shown as with a radius to its trailing end. The pumping efficiency of the vane faces 52 is accordingly somewhat less than the vane faces 38.

In accordance with the invention, therefore, the rotor 50 is provided with pumping vanes 55 similar in axial view with the pumping vanes 40 but of somewhat greater axial dimensions. For example, in such a rotor having an overall diameter of 63 inches, the defibering vanes may have an axial dimension of 1.25 inches adjacent their trailing edge while the pumping vanes 55 have an axial dimension ranging from 4 inches at their trailing edges to zero at the points where they fair into the body of the rotor. The angular relation of their vanes to the rotor body establishes the angle a as very close to 45, and their pumping efficiency therefore approaches the optimum.

The rotor 50 is also shown as provided with an inner set of four pumping vanes 58 having an axial dimension ranging from 3 inches at their trailing ends to zero at their radially inner ends. The purpose of these vanes 58 is primarily to prevent large pieces of material from becoming trapped in the vortex by the vanes 55 and thereby failing to reach the defibering zone.

Rotors constructed as shown in FIGS. 8-9 have proved to be so effective and efficient, from the standpoint of the pumping action of the vanes 55 and 58, that for larger rotors, the same vane arrangement can be used even if the defibering vanes are extended in length. Such an arrangement is illustrated in FIG. 10, wherein the fragment of the rotor is shown as of the same construction as in FIGS. 89 except that the defibering vanes 61 are further extended, for example to an outer diameter of 81 inches. It will be noted that with this extended vane construction having the same angular relation with the rotor body as in FIG. 8, the leading face 62 of each vane 61 will form with a radius to its trailing edge an angle c smaller than 20, so that the pumping efficiency of the faces 62 will be even lower than for the vane faces 52 in FIG. 8. Nevertheless, the same arrangement and dimensions of pumping vanes 65 and 66 can be used on this rotor as shown for the rotor 55, the pumping efficiency of this vane arrangement being such that it requires no supplementing on the larger rotor.

While the curved pumping vanes shown in FIGS. 3, 8 and 10 are advantageous for smooth operation, it is also possible in accordance with the invention to utilize straight pumping vanes, which offer some advantages from the standpoint of ease of fabrication. FIG. 11 shows such an arrangement, wherein the fragment of a rotor 70 includes defibering vanes 71 of the same construction described in connection with FIG. 3 and a pumping vane comprising an outer section 72 arranged for the most effective pumping action, namely defining an angle b ofapproximately 45 with a radius to its trailing end 75, and an inner section 73 the primary purpose of which is to complete the vane without a leading edge on which elongated materials could hang up. Note that this arrangement makes it possible and practical to have the outer pumping vane section 72 define angles close to 45 with radii thereto.

It is also not essential to the practice of the invention that the defibering vanes have flat leading faces, so long as the leading face of each defibering vane is essentially straight and includes a portion diverging from the under surface ofthe vane which will urge stock into the space between the vane and the cooperating bedplate. Such a modified construction is shown in FIG. I2, wherein the vane has a flat under surface 81, and its leading face is beveled in section to provide a forwardly inclined lower portion 82 and a rearwardly inclined upper portion 83. This construction offers the further advantage that it minimizes the pumping action of the defibering vanes and thus further contributes to minimizing power which would otherwise be lost by reason of the pumping inefficiency of the defibering vanes, and similar effects could be obtained with a bull nosed leading edge on each defibering vane.

While the forms of apparatus herein described constitutes preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention.

What is claimed is:

1. A rotor assembly for use in pulping apparatus of the character described for liquid slurry stock including a tub for receiving a quantity of stock and a bedplate mounted in the tub and having a working surface, comprising:

a. a rotor body adapted to be mounted for rotation in predetermined direction in cooperative relation with the bedplate and having a plurality of defibering vanes projecting outwardly therefrom in angularly spaced relation,

b. each of said vanes having under and upper surface portions of substantial area,

c. means forming an essentially straight leading face on each of said vanes connecting said upper and under surfaces thereof.

d. the outer edge of said face extending in said direc tion of rotation from a radius to the radially outer end thereof and defining with said radius a first angle of substantially less than 45, and

e. a plurality of pumping vanes each mounted on said upper surface portion of one of said defibering vanes and of such curved configuration as viewed axially of said rotor body that a second angle defined by a radius to said radially outer end thereof and a tangent to said outer end is sufficiently larger than said first angle to promote efficient vortical circulation of the liquid slurry stock.

2. A rotor assembly as defined in claim I wherein said first angle is not greater than 30 and said second angle is closer to 45 than said first angle.

3. A rotor assembly as defined in claim 1 wherein the leading end of each said pumping vane is substantially tangent to the leading end of said leading face on the associated said defibering vane and the trailing end thereof overlies the trailing outer corner of said associated defibering vane.

4. A rotor assembly as defined in claim 1 comprising a plurality of supplemental pumping vanes located radially inwardly of said pumping vanes on said defibering vanes for dislodging solid materials from the center of the vortex created by said rotor assembly.

5. A rotor assembly as defined in claim 1 wherein the axial dimensions of said defibcring vanes are substantially less than the axial dimensions of said pumping vanes to minimize the pumping action of said leading faces of said defibering vanes and the power required thereby.

6. A rotor assembly for use in pulping apparatus of the character described for liquid slurry stock including a tub for receiving a quantity of stock and a bedplate mounted in the tub and having a working surface. comprising:

a. a rotor body adapted to be mounted for rotation in predetermined direction in cooperative relation with the bedplate and having a plurality of defiber ing vanes projecting outwardly therefrom in angularly spaced relation,

b. each of said vanes having upper and outer surface portions of substantial area,

c. means forming an essentially straight leading face on each of said vanes connecting said outer and under surfaces thereof,

d. the outer edge of said face extending in said direction of rotation from a radius to the radially outer end thereof and defining with said radius a first angle of substantially less than 45, and

e. a plurality of pumping vanes each mounted on said upper surface portion of one of said defibering vanes and of such straight configuration as viewed axially of said rotor body such that a second angle defined by said pumping vane a radius to said radially outer end thereofis sufficiently larger than said first angle to promote efficient vortical circulation of the liquid slurry stock. 

1. A rotor assembly for use in pulping apparatus of the character described for liquid slurry stock including a tub for receiving a quantity of stock and a bedplate mounted in the tub and having a working surface, comprising: a. a rotor body adapted to be mounted for rotation in predetermined direction in cooperative relation with the bedplate and having a plurality of defibering vanes projecting outwardly therefrom in angularly spaced relation, b. each of said vanes having under and upper surface portions of substantial area, c. means forming an essentially straight leading face on each of said vanes connecting said upper and under surfaces thereof, d. the outer edge of said face extending in said direction of rotation from a radius to the radially outer end thereof and defining with said radius a first angle of substantially less than 45*, and e. a plurality of pumping vanes each mounted on said upper surface portion of one of said defibering vanes and of such curved configuration as viewed axially of said rotor body that a second angle defined by a radius to said radially outer end thereof and a tangent to said outer end is sufficiently larger than said first angle to promote efficient vortical circulation of the liquid slurry stock.
 2. A rotor assembly as defined in claim 1 wherein said first angle is not greater than 30* and said second angle is closer to 45* than said first angle.
 3. A rotor assembly as defined in claim 1 wherein the leading end of each said pumping vane is substantially tangent to the leading end of said leading face on the associated said defibering vane and the trailing end thereof overlies the trailing outer corner of said associated defibering vane.
 4. A rotor assembly as defined in claim 1 comprising a plurality of supplemental pumping vanes located radially inwardly of said pumping vanes on said defibering vanes for dislodging solid materials from the center of the vortex created by said rotor assembly.
 5. A rotor assembly as defined in claim 1 wherein the axial dimensions of said defibering vanes are substantially less than the axial dimensions of said pumping vanes to minimize the pumping action of said leading faces of said defibering vanes and the power required thereby.
 6. A rotor assembly for use in pulping apparatus of the character described for liquid slurry stock including a tub for receiving a quantity of stock and a bedplate mounted in the tub and having a working surface, comprising: a. a rotor body adapted to be mounted for rotation in predetermined direction in cooperative relation with the bedplAte and having a plurality of defibering vanes projecting outwardly therefrom in angularly spaced relation, b. each of said vanes having upper and outer surface portions of substantial area, c. means forming an essentially straight leading face on each of said vanes connecting said outer and under surfaces thereof, d. the outer edge of said face extending in said direction of rotation from a radius to the radially outer end thereof and defining with said radius a first angle of substantially less than 45*, and e. a plurality of pumping vanes each mounted on said upper surface portion of one of said defibering vanes and of such straight configuration as viewed axially of said rotor body such that a second angle defined by said pumping vane a radius to said radially outer end thereof is sufficiently larger than said first angle to promote efficient vortical circulation of the liquid slurry stock. 